Re: Z channel on Tempest?

The short answer is that the Z channels of Tempest, which are the R,G,B signals, are analog. Chucking them through a
logic gate is not likely going to benefit you. Not only is all of the intensity information lost, it doesn't mix the 3
signals into a single mono signal. Logically, they could be all OR'd together but the best performance you could hope
for is on/off, a single intensity trace on your scope that represents any and all colors. Maybe for your scope test,
that's enough however. The point is, a mono scope can really only test 1 color output at a time. Viewing just one color
at a time won't likely produce a complete picture but there would be a chance that you could see variable intensity
(unless it is logically gated to be on/off only).

Colorwise, two of the signals have a single on/off control and the third (red on Tempest, green on Quantum) has two. If
all three (R,G,B) had 1 level, there would be 7 colors but since 1 of them has 2 levels, that means there's 14 colors.
Besides the 14 basic colors, there's 16 intensity levels of each of those. Altogether, this provides 224 combinations
not counting all blanked.

To connect the R,G,B to a scope and display it as a mono signal, you would have to use a mixer circuit. Such can be a
simple network of resistors but ideally an op-amp would be included. Fortunately on Tempest, such a resistor network
already exists and there is a B/W Video output. Try using that signal as Z to your scope.

If you have to invert the B/W output and maintain its analog behavior, an inverting amplifier is needed. A unity gain
inverter running from a +-12V supply would accomodate this but the +1V to +4V output would become -1V to -4V. To get
this response moved up to +4V to +1V, the op-amp must add a positive offset of +5V. This is super easy basic beginner's
op-amp stuff that is literally all over the internet presented as op-amp tutorials. I could provide a circuit
schematic.

Bill Boucher
http://www.biltronix.com

>
> Thanks. I am still pretty new at this; would you be so kind as to share how it's hooked up? I thought Z was used for
> intensity levels as well as blanking; ie, it was analog. Do you discard them and live with on/off?
>
> -Douglas
>
> On Jan 19, 2012, at 9:48 PM, Joel Rosenzweig wrote:
>
> > I used a 7400 chip to invert the Z axis blanking signal for Tek scopes. Worked great.
> >
> > Joel
> >
> > On Jan 19, 2012, at 9:44 PM, Ken Sumrall wrote:
> >
> >> Can you use an op-amp in a unity gain inverter configuration? You'd need something faster than a 741, but that's
> not hard to find. >>
> >> ___
> >> Ken
> >>
> >>
> >> On 01/19/2012 03:10 PM, douglas@gauck.com wrote:
> >>> Anybody have an inverting circuit already designed? I found chips and
> >>> circuits that will output the opposite voltage (ie +5v in gives -5v out)
> >>> but for Asteroids, at least, the Z out swings from +1v to +4v. How to
> >>> change that to +4v to +1v? Or am I missing something?
> >>>
> >>> -Douglas
> >>>
> >>> On Oct 3, 2011, at 12:09 PM, David Shoemaker<davids@oz.net> wrote:
> >>>
> >>>> My Tek 2215a says 5v has appreciable cutoff. So I will need to invert.
> >>> From: Joel Rosenzweig
> >>>> Sent: Monday, October 03, 2011 7:35 AM
> >>>> To: vectorlist@vectorlist.org
> >>>> Subject: Re: VECTOR: Z channel on Tempest?
> >>>> Check the polarity of the z axis blanking signal. You may need to
> >>> invert it.
> >>>> Sent from my iPhone
> >>>> On Oct 3, 2011, at 10:07 AM, Douglas Gauck<douglas@gauck.com> wrote:
> >>>>> It may be simple for David but I can't seem to get either of my scopes
> >>> (Tek 475A and 2465B) to pay enough attention to the Z signal to blank the
> >>> repositioning vectors. There is a barely perceptible decrease in intensity
> >>> when I hook it up but they're still visible. What's the
> >>> proper way to connect for blanking?
> >>>>> -Douglas
> >>>>> On Oct 3, 2011, at 1:06 AM, "David Shoemaker"<davids@oz.net> wrote:
> >>>>>> I am benching testing a couple of tempest boards on my Scope and have
> >>> lots of retrace vectors cluttering up the display.
> >>>>>> When doing a BZ it is simple to hook up the z input of the scope to
> >>> the intensity signal and get a pretty good picture.
> >>>>>> BUT of course on tempest there are 3 intensities. Has anyone ever
> >>> come up with a nice simple circuit to build a unified intensity
> >>> channel for this kind of use?
> >>>>>> Thanks,
> >>>>>> David
> >>>
> >>>
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Received on Wed Jan 25 12:49:40 2012